The first polyalanine tract found in exon 2 was expanded by the insertion 8 GCT alanine tracts bringing the total number of alanine codons in tract 1 to 23. In addition loxP sites were inserted around exon 2 and an frt flanked neo cassette was inserted in intron 2 via homologous recombination. Flp mediated recombination then removed the neo cassette. (J:151082)